1. Field of the Invention
The present invention relates to a delay storage device which is provided at a stage preceding a processor for sequentially performing a process at a request from a user, temporarily stores the processing request while sequentially inputting a large number of quickly received processing requests to a processor at a subsequent stage, and controls the transfer rate of processing requests depending on the request of a user and the performance of the processor at the subsequent stage, and also relates to a delay treating method.
2. Description of the Related Art
In the processor of the conventional Web server, etc., a round robin technology is used to provide a domain name server (DNS) for allocating processing requests to a plurality of processors to reduce the load of a system, and relay a processing request from a user (for example, non-patent document 1 and patent document 1). In this technology, a plurality of servers are virtually recognized by a client as one server, but actually a processing request is allocated to a plurality of servers.
There is another technology of providing a device called a proxy server between a user and a processor, recording a processing request from a user, and also recording a processing result from a processor (for example, patent document 2). In this technology, when the same processing request is issued from the same or another user again, a recorded processing result can be returned to a user as a processing result of the processor at a subsequent processor without relaying the processing request to the processor at the subsequent stage.
Non-patent Document 1
“Structuring a High-Performance and Availability Cluster System”, on page 3, 1.1, Type of Load Balancing, [online], Jun. 16, 2000, Zeus Technology, Technical Material, Technical Information, [retrieved on Mar. 7, 2003], Internet<URL: http://www.jp.zeus.com/library/technical/cluster/in dex.html>
Patent Document 1
Japanese Published Patent Application No. 2002-057691
Patent Document 2
Japanese Published Patent Application No. 2002-259338
However, the above-mentioned conventional technology has the following problems.
With the conventional round robin technology, when all of a plurality of processors to be allocated enter in a high load status, a processing request from a user is kept waiting without an answer.
Also, with a proxy technology, since the processing result for the initially accepted processing request is not recorded, the processing request is transmitted to a subsequent processor as is. Therefore, when a subsequent processor is in a high load status, a processing request from a user is kept waiting without any answer even if a proxy server is allocated.
Actually, an upper limit of the performance (for example, the number of processes per unit time) of the processor at a subsequent processor is determined in many cases. Therefore, when the number of processing requests exceeds the upper limit, the processor overflows, and a delay occurs in processing time.